Adding check in requestPermissions for pre M apps

The recent optimization introduced in ag/30469303 is
causing PermissionTest22#testNoRuntimePrompt test to
fail. The test is verifying that permission dialog
is not shown for pre M apps i.e. target sdk < 23.

Although these apps are not supposed to call
Activity#requestPermissions API, adding this
check for compatibility.

Fix: 384177995
Test: atest PermissionTest22
FLAG: EXEMPT test fix

Change-Id: I34aa955fc13a2c0758fe2726467fc5082d72d2c4